I. Field of the Invention
This invention relates to spiral wound gaskets for sealing between connected flanges of pipe sections and, in particular, to a spiral wound gasket which reduces inward buckling of the spiral winding upon application of clamping pressure between the pipe flanges.
II. Description of the Prior Art
Spiral wound gaskets are extensively used in the petroleum industry to seal between sections of pipe connected by their end flanges. A series of bolts are used to tie the flanges together by applying a predetermined stress to the bolts. A spiral wound gasket is positioned between the pipe flanges to eliminate fluid leakage between the flanges. The typical spiral wound gasket comprises a winding of metal and an outer guide ring. The winding has a thickness greater than the thickness of the guide ring such that the winding can be compressed between the flanges while the metal guide ring acts as a stop against further compression. Despite the compression limit provided by the guide ring, deformation of the winding can occur as the gasket is being compressed between the flanges.
As the spiral wound gasket is compressed, the winding, which comprises spiral wound layers of metal with a sealing material therebetween for improved sealing, will be laterally compressed under the force of the flanges. The clamping force causes the sealing material to flow between the metal windings attempting to find an outlet while creating a sealing surface. With lateral flow prevented by the flanges of the pipe and diametrically outward flow prevented the guide ring, the sealing material may eventually cause the windings to buckle inwardly into the pipe chamber. Buckling of the winding causes two immediate problems: first, the sealing capabilities of the gasket are compromised and, second, the protrusions disrupt the flow of fluids through the pipe.
One means of eliminating inward buckling is to attach a solid inner ring on the inside diameter of the winding. However, the inner ring significantly increases the cost of the gasket.